The past decade has seen a great increase in patients wearing prescription contact lenses and color contact lenses in order to correct visual sensation and change appearance of eyes. The advancement in silicone-hydrogel composite technology has improved both the water affinity and oxygen permeability of a contact lens and transformed it into a breathable and hydrophilic soft tissue. Integrating this hydrophobic-hydrophilic nanocomposite technology with other advancements in materials and medical nanotechnology, we can develop a new generation of nanoengineered ocular device that has the same optical performance and ease of use as a contact lens, but with many more medical applications beyond simple vision correction. Because such an ocular device is in constant contact with tear fluids at the most observable location of the eye, and is easily applied and removed, it can function as the most convenient implantable medical device for diagnostics, drug delivery, wound healing, and in particular, as a groundbreaking tool in ocular disease therapy.
Delivering a drug to the eye at high therapeutic efficacy is challenging due to the eye's complexity, including high sensitivity to foreign stimuli, protective mechanisms (e.g., blinking, tears), and several overlaying diffusion barricades (Short B, Soc Toxicol Pathol 2008; 36: 49-62). The two main alternatives to implants have serious limitations and drawbacks as follows.
1. Topical application of eye drops results in a sudden, burst dosage that is difficult to control, and further hindered by tear drainage along with corneal and scleral barriers to the point that only about 5% of functional ingredients deliver to the target, and
2. Intravitreal injection, while direct and efficacious, also gives a burst dosage that raises intraocular pressure, and requires repeated administration that bears risks to the patient's eye including hemorrhage, cataract, retinal wounds and even retinal detachment.
There is a need for an ocular device that can effectively deliver a drug to the eye and release the drug at a dosage rate that is precisely controllable and sustainable.